There are still many challenges in designing drug delivery systems for treating colon-related diseases such as irritable bowel syndrome, Crohn's disease and ulcerative colitis. To ensure its delivery to the colon tissue, an oral drug needs to be formulated to be resistant to stomach acid and minimize intestinal release before it reaches the colon. The major formulations of colonic drug delivery systems developed during the past decade have been based on time-dependent release, pH-sensitive polymer coatings, and prodrug systems.
The time-dependent-release formulation is designed to delay the onset of the drug release until it reaches the colon. This kind of formulation suffers from the disadvantage that a precise control of colon site-specific release is not easy to achieve because the transit time from the mouth to the colon is variable. The pH-dependent release formulation is based on the different pH values in various segments of the GI tract. This kind of formulation has the disadvantage that the drug, although successfully passing through the stomach, is prematurely released in the small intestine because the pH of the small intestine and colon are not significantly different. The prodrug formulation is based on the presence of bacteria in the colon (about 1012 CFU/mL), which catalyze reactions that convert a prodrug into an active drug. This strategy suffers from the disadvantage that a portion of the prodrug is converted into the active form in the stomach and small intestine, which contain lower amounts of the same bacteria (about 104 CFU/mL).
Mesoporous silica nanoparticles (MSN) have been used to incorporate large dosages of hydrophobic drugs inside their nanochannels. They have also been used to incorporate a contrast agent for in vivo cell tracking purposes. Although MSN are useful in carrying drug molecules, its loading capacity and use for controlled drug release have been a challenge for developing good bioavailability and site-specific drug delivery system.
A previously unaddressed need exists in the art to address the deficiencies and inadequacies, especially in connection with establishment of a good bioavailability and controlled release drug delivery system.